Pressure vessels are used in many industry sectors for the high-pressure storage of fluids. These fluids are primarily gaseous. In industries where weight is not a major concern, these pressure vessels are frequently made from monolithic materials, such as metals. In other industries such as aerospace, vehicles, and emergency first responders, the weight of a pressure vessel is critical to its functionality. In these areas, composite pressure vessels provide a unique advantage. The ability to construct the vessel with the mechanical properties of the material directionally aligned with the stresses in the vessel allows for greatly decrease weight.
One frequently employed method for the fabrication of composite pressure vessels is filament winding. In filament winding one or more strands of fiber, (e.g., carbon, glass, aramid) is impregnated with resin and then wound into the shape of a pressure vessel and cured. To obtain the shape of the pressure vessel, fabricators typically use a mandrel, also known as a liner. The liner provides the base geometry of the vessel, provides provisions for valve and or fitting attachments, and serves as a bladder for fluids in the finished vessel. Pressure vessel liners are typically made from metals with thin walls that could not handle the pressure load without the composite overwrap, known as type-3 vessels. Liners may also be constructed from plastics with metallic boss (port) fittings attached to the plastic. Plastic liners are used in pressure vessels for cost savings and decreased weight. Such vessels require a metallic port for attachment of fittings that enable filling and discharging the vessel, as well as containing the pressure. The sealing of the metallic boss to the plastic liner can be a challenging task when the vessel contains a gaseous fluid at high pressure and the vessel must operate over a large temperature range such as −40° F. to 185° F.
Accordingly, there is a continued need in the art for affordable and efficient high-pressure vessels that enable sealing of the boss to the plastic liner.